Sol-gel TiO2 films were deposited from various sols and heat-treated at different temperatures. Fourier transform infrared spectroscopy, ellipsometry, X-ray diffraction, and scanning electron microscopy methods have been used to study physico-structural properties of the films. These properties are discussed with respect to the experimental parameters. It is shown that, depending on sol formulations and annealing temperatures, a large range of crystallite size, crystallization degree, film porosity, and surface morphology can be covered. The photocatalytic properties of the films have been studied in relation to their physico-structural properties through the photodecomposition of malic acid. This study shows that the photocatalytic activity undergoes a complex dependence on the physico-structural properties. (c) 2006 Springer Science + Business Media, Inc.